Estimation of the Nutritional Efficiency of Azolla Plant for Common Carp Fish (Cyprinus carpio)

Background: The experiment was carried out in glass aquaria (100 × 40 × 40 cm) with juveniles of common carp (Cyprinus carpio L.) that were obtained from a local fish breeder in Jadidat Al-Shatt, Diyala Governorate, from 25 October 2024 until 5 January 2025. Each aquarium was stocked with 10 fish and three replicates per each treatment. The treatments consisted of commercial feed that contained 35.58% crude protein (control), second one with 80% commercial feed and 20% dried Azolla, third group with 80% commercial feed and 20% fresh Azolla. The fish were fed at the rate of 5% of their weight (total biomass) in 3 meals a day with the feed amount being adjusted every two weeks. Water was changed every two days (replaced 70% of total aquarium water) using clean water.Aims: The planned study was designed to assess the potential for Azolla to serve as a partial protein substitute in carp diets and to check their impacts on growth rate, growth and relative growth rate. Results: The statistical analysis indicated that a significant difference was found among the treatments as the fresh Azolla treatment significantly resulted in the highest weight gain (3.48 g. fish⁻¹) among all treatments compared to dried Azolla (2.36 g. fish⁻¹) and control treatment (1.94 g. fish⁻¹). Similarly, for growth rate, the dried Azolla treatment had the highest growth rate (67.50 g. fish⁻¹), which was significantly greater than the control treatment (39.00 g. fish⁻¹). The diet based on dried Azolla also resulted in the highest relative growth rate (245.88%) compared to the fresh Azolla treatment (161.10%). In addition, the dried Azolla treatment had the best feed conversion ratio of 2.935 g. fish⁻¹ when compared to control and fresh Azolla treatment (3.250 and 3.343 g. fish⁻¹ respectively). Conclusions: In conclusion, the study found that feeding common carp diets with Azolla improved growth performance when compared to feeding commercial feed only.